National Toxicology Program

National Toxicology Program

Validation of the BG1Luc Estrogen Receptor Transactivation Test Method

Change in Assay Designation (June 2016)

In June 2016, NICEATM received new information regarding the BG1Luc estrogen receptor (ER) transactivation (LUMI-CELL®) assay (TA). DNA testing has now shown that the original cell line used to develop the assay was not the BG1 human ovarian carcinoma cell line, but was instead a variant of the MCF7 human breast cancer cell line. The cell line used in the assay, originally referred to as BG1Luc4E2 (Rogers and Denison, 2000), will now be designated as VM7Luc4E2 (“V” = variant; “M7” = MCF7 cells). Likewise, the assay will now be designated as the VM7Luc ER TA. While this changes the origin of the cell line upon which the assay is based, it does not affect published validation studies nor the utility and application of this assay for screening of estrogenic/anti-estrogenic chemicals.

This correction should accompany any information currently referencing the BG1Luc ER TA (e.g., webpages, databases, documents, manuscripts).

Supporting Documentation from Michael Denison, Department of Environmental Toxicology, University of California, Davis

Summary of Test Method Evaluation and Acceptance

In their responses to a 2012 ICCVAM report, U.S. Federal agencies agreed with ICCVAM recommendations on the use of human cell-based test methods to screen for substances with the potential to interact with the estrogen receptor.

ICCVAM evaluated the scientific validity of the BG1Luc ER TA agonist and antagonist assays and recommended how they could be used as a screening test to identify substances that induce or inhibit human ER activity in vitro. The U.S. Environmental Protection Agency (EPA) responded that they regard the BG1Luc ER TA test method as an alternative to the ER TA test method used in their Endocrine Disruptor Screening Program. Several other Federal agencies indicated that they would communicate the ICCVAM recommendations to stakeholders and encourage appropriate use of the recommended methods.

Test Method Evaluation Report (February 2012) with ICCVAM recommendations

ICCVAM developed the recommendations on the BG1Luc ER TA assays after considering the comments of a 2011 international independent peer review panel, as well as comments from the public and the Scientific Advisory Committee on Alternative Toxicological Methods. ICCVAM concluded that the accuracy of the BG1 ER TA agonist assay is at least equivalent to the only ER TA test method in a U.S. regulatory test guideline, the EPA’s “OPPTS 890.1300: Estrogen Receptor Transcriptional Activation (Human Cell Line (HeLa-9903)).” The BG1Luc ER TA assays offer several advantages over the existing ER TA method, including (1) validation for use over a wider concentration range of test substances, (2) potential to detect a wider range of ER-active substances, (3) ability to identify both substances that induce and inhibit the estrogen receptor, and (4) availability of the cell line used for the test from more than one source.

See below for letters to Federal agencies communicating ICCVAM recommendations and agency responses

Background on the Validation Study

The BG1Luc ER TA test method (also known as the LUMI-CELL® test method) was developed by Xenobiotic Detection Systems, Inc., with support from NIEHS Small Business Innovation Research grant ES10533-03. The test method measures the extent to which a substance induces or inhibits TA activity via ER-mediated pathways in recombinant BG1Luc4E2 cells.

The BG1Luc4E2 cell line was derived from BG-1 immortalized adenocarcinoma cells that endogenously express both human ER forms, ERα and ERβ, and that have been stably transfected with the plasmid pGudLuc7.ERE. This plasmid contains four copies of a synthetic oligonucleotide containing the estrogen response element upstream of the mouse mammary tumor viral promoter and the firefly luciferase gene. BG-1Luc4E2 cells emit measurable light in response to estrogen and estrogen-like substances.

NICEATM coordinated an international interlaboratory validation study to evaluate the BG1Luc ER TA test method. The study included participating laboratories in the U.S., Italy, and Japan. It was the first validation study sponsored jointly by ICCVAM, the European Centre for the Validation of Alternative Methods (now known as the European Union Reference Laboratory for Alternatives to Animal Testing), and the Japanese Center for the Validation of Alternative Methods.

Peer Review of the Validation Study

An independent international peer review panel (2011) agreed with the ICCVAM draft test method recommendations that an in vitro test method may be used as an initial screen to identify substances with the potential to enhance or inhibit activation of the estrogen receptor. The panel of 16 expert scientists from six countries reviewed data from the validation study, made recommendations on future studies that could further enhance the usefulness of the BG1Luc ER TA test method, and commented on draft performance standards that could be used to expedite the evaluation of similar test methods.

Read the peer review panel report (May 2011) 

Corrections to the Peer Review Panel Report (August 2011) 
This document lists changes made to the report by the peer review panel members that were inadvertently omitted in the printed version of the report. The electronic version of the report available above includes these corrections. If you have a printed copy of this report, please print this document and keep it with the printed report. We apologize for any inconvenience.

Read a summary of the March 2011 peer review panel meeting

BG1Luc Estrogen Receptor Transactivation Test Method in the Tox21 Program

NICEATM nominated the BG1Luc ER TA agonist and antagonist assays for evaluation and adoption by the Tox21 program. The assays have now been translated to a high throughput format using 1536-well plates by the National Center for Advancing Translational Sciences and have been used to screen all compounds in the Tox21 10K chemical library. More about NICEATM support of the Tox21 program

Transmittal of Recommendations to Federal Agencies

Other Materials Relevant to the Validation Study

Test Method Nomination: Submission of XDS’s LUMI-CELL® ER High-Throughput System for Screening Estrogen-Like Chemicals for Review by ICCVAM (February 2005)

Draft Evaluation: Nomination of the LUMI-CELL® ER High-Throughput System for Screening Estrogen-Like Chemicals for Validation Studies (August 2004)

Protocols for the International Validation Study:

NTP is located at the National Institute of Environmental Health Sciences, part of the National Institutes of Health.